In a throttle opening detection apparatus, when a rider of a motorcycle operates to rotate a throttle grip, an electrically operated throttle valve is operated not by a mechanical movement of a cable connecting to the throttle grip but directly in response to an electric signal from a sensor. This sensor electrically detects an amount of the rotation of the throttle grip. Such an apparatus is generally described in Japanese Patent No. 2,902,490 (hereinafter “Patent Document 1”). In this instance, since distortion, elongation and friction of a cable are not involved, the rotation load of the throttle grip by the rider decreases, and the throttle grip can be operated to rotate by very light operating force. However, a suitable load to adjust the amount of rotation of the throttle grip is preferable.
Japanese Patent No. 4,112,876 (hereinafter “Patent Document 2”) generally describes a throttle opening detection apparatus that includes a resisting force application means. The resisting force application means generates a rotation load of a throttle grip by frictional force. The frictional force is generated when a friction plate is pressed against a gear wheel which forms part of a gear mechanism. The gear mechanism is provided between the throttle grip and a throttle sensor and is accommodated in a case together with the throttle sensor.
Japanese Patent Laid-Open No. 2007-270783 generally describes a throttle opening detection apparatus for a saddle-type vehicle such as a motorcycle. The saddle-type vehicle includes an auto-cruise controlling apparatus that automatically keeps a traveling speed at a fixed speed without a throttle operation by a rider. The saddle-type vehicle also includes a cancel switch capable of canceling the operation of the auto-cruise controlling apparatus.